Copper (1) precursors for chemical deposit in gas phase of metallic copper

ABSTRACT

The invention concerns complex compounds of oxidised copper (+1) stabilised by a ligand for the gas phase chemical deposit of copper in which copper is coordinated with a β-diketonate and the ligand is an alkyne of which the triple bond is partially deactivated by one or two groups slightly attracting the electrons by said alkyne.

The present invention relates to the chemical deposit method in gasphase of pure metals such as copper and silver, in the electronicsindustry, for the production of integrated circuits. This method, calledCVD for "Chemical Vapor Deposition" is widely used to produce, fromprecursors of said metals in oxidised form (+1), the interconnectionsand metallisation of integrated circuits measuring 0.25 μm or less.

Numerous copper precursors are known in the prior art for thefabrication of films made up of said pure metal. The most promisingprecursors are complex compounds of oxidised copper (+1) stabilised by aligand in which the copper is compounded with a β-diketonate having thefollowing general formula: ##STR1## in which R, R' and R", identical ordifferent, are chosen from among a hydrogen atom, a halogen atom such asfluorine, a lower alkyl optionally substituted by one or more fluorineatoms.

Preferred complexes are those in which R is a hydrogen atom and R' andR" are perfluorine alkyls, advantageously --CF₃ groups meeting thefollowing structural formula: ##STR2##

Such complexes and the way they are used in the CVD method are, forexample, described in U.S. Pat. Nos. 5,085,731, 5,096,737, 5,098,516,5,144,049, 5,187,300 whose teaching on the CVD method is incorporatedherein by reference.

The work conducted on these precursors demonstrates that their molecularstructure is decisive for the reproducible production of films of goodquality (P. Doppelt and T. H. Baum, MRS Bull. XIX(8) 41, 1994). However,the electronics industry does not have available an ideal precursor forthe reproducible fabrication of electronic circuits containing thincopper films to enable defect-free filling of vertical lines andinterconnections that offers low resistivity and good long term thermalstability.

As reported in the above-mentioned patents, the formation of metalliccopper results from the dismutation of two copper molecules (I) on asurface heated to a temperature close to 200° C. in accordance with thefollowing reaction:

    2Cu(I)(hfac)L→Cu(II)(hfac)2+Cu(O)+2L

The nature of the Lewis base L, also called hereafter the ligand, onlyslightly influences the nature of the copper films obtained by CVD.Copper films are generally very pure, free of carbon or oxygen atoms(less than 1%), and resistivity in the region of 1.8 μΩ is frequentlyfound in copper films obtained by CVD; this value is very close to theone found in solid copper (1.67 μΩ.cm). On the other hand, the nature ofligand L determines the volatility of the complex and consequently therate of deposit of the copper obtained.

In the prior art, more than 80 copper complexes (I) (hfac) are knownwhich have been tested for the CVD of copper, such as for example:

carbon monoxide, isonitrile, unsaturated hydrocarbon ligands, comprisingat least one non-aromatic insaturation cited in U.S. Pat. No. 5,098,516;

alkynes and acetylene derivatives, dienes, olefins and phosphines, citedin U.S. Pat. No. 5,096,737;

the compounds cited in U.S. Pat. No. 5,144,049 meeting the formula:

    C(R.sup.4)(R.sup.5)═C(R.sup.5)Si(R.sup.6).sub.3

in which R⁴, R⁵ and R⁶ are hydrogen atoms or lower alkyls at C₁ to C₈.

the compounds cited in U.S. Pat. No. 5,187,300 meeting the formula:

    R4C--C.tbd.Si(R.sup.5)3

in which R⁴ and R⁵ are lower alkyls at C₁ to C₈.

The three copper precursors for CVD, liquid at ambient temperature,given in Table I below have been the subject of particular study:

                  TABLE I                                                         ______________________________________                                        Precursors          Volatility                                                ______________________________________                                                              Very volatile up to  200 nm/min (H                                          .sub.2 O)                                                    -                                                                                                Scarcely volatile:  140 nm/min                             -                                                                                                Very volatile up to  400 nm/min. Formation  of a                            less volatile  secondary product                          ______________________________________                                    

Among the latter, the (3-hexyne) Cu(hfac) complex is the one which givesthe highest growth rate. On the other hand, it has recently been shownthat it leads to the formation of dinuclear complexes which form a majorobstacle to its use (P. Doppelt and T. H. Baum, Journal ofOrganometallic Chemistry 517, 53-62, 1996).

In order to remedy this disadvantage, the inventors have examinedelectronic phenomena related to the formation of dinuclear complexesduring the use of a copper complex for CVD stabilised by a ligand madeup of an alkyne whether substituted or not. Research work conducted hasbeen able to demonstrate that the formation of these dinuclear speciesis helped when the alkyne carries electron-donor groups, such as forexample the Si(R)₃ group described in U.S. Pat. No. 5,187,300.

The present invention sets out precisely to provide a solution to theproblem raised by the formation of dinuclear complexes during the use ofa copper complex stabilised by a ligand of triple bond carrying type,while maintaining the potentialities of the precursor for CVD. Thisobjective is reached by using ligands in which the triple bond ispartially deactivated by one or two groups slightly attractingelectrons, such as a double bond or one or two alkoxy groups with theformula --O--(CH₂)n--CH₃ in which n is 0 up to the order of 8 and isadvantageously a methoxy group (--O--CH₃).

The invention therefore relates to organometallic complexes that areliquid volatile or solid with low melting point, also called hereaftercopper precursors (I) for gas phase chemical deposit having the generalformula (I): ##STR6## in which R' and R", identical or different, are alower alkyl optionally substituted by one or more halogen atoms such asfluorine, R is chosen from among a hydrogen atom, a halogen atom such asfluorine, a lower alkyl optionally substituted by one or more halogenatoms such as fluorine, and L represents the stabilising ligand of saidcomplex characterized in that L is an alkyne whose triple bond ispartially deactivated by one or two groups slightly attracting theelectrons carried by said alkyne.

When L is an alkyne of which the triple bond is partially deactivated bytwo slightly electron-attracting groups, it is preferred that the latterbe arranged either side of said triple bond.

One ligand of the invention meets the following formula (II): ##STR7##or the following formula (III): ##STR8## or the following formula (IV):##STR9## in which R₁, R₂, R₃ and R₄, identical or different, are chosenfrom among a hydrogen atom, a lower alkyl substituted by one or morefluorine atoms, a --Si (R₅)₃ group in which R₅ is a lower alkyl, i and jare 0 to 3 and X₁ and X₂, identical or different, represent a group thatis slightly electron-attracting.

One first group of preferred ligands of the invention are alkene-ynes,that is to say compounds comprising one or two double bonds and onetriple bond. These ligands are those with the formula (II), (III) or(IV) in which X₁ and X₂ identical or different are radicals with thefollowing formula (V): ##STR10## in which R₆, R₇ and R₈ are chosen fromamong a hydrogen atom, a lower alkyl substituted by one or more fluorineatoms, a Si(R₅)₃ group in which R₅ is a lower alkyl, or in which R₆ andR₂ together or R₆ and R₁ together, or two R₆ radicals together, form agroup having the formula (VI): ##STR11## in which R₉ and R₁₀ are chosenfrom among a hydrogen atom, a lower alkyl substituted by one or morefluorine atoms, a Si(R₅)₃ group in which R₅ is a lower alkyl, and k is 1to 3, such as to form ligands with cyclical formulas, such as forexample: ##STR12## in which R₃, R₄, R₆, R₇, R₈, R₉, R₁₀, i and k havethe same denotation as in formulas (II), (V) and (VI).

Among the formula (IV) compounds in which X₁ and X₂ are of formula (V),preference is given to those in which i or j is different from 0, suchas to avoid combining of the double bonds and the triple bond.

Among the compounds of formulas (II) or (III), particular preference isgiven to:

2-methyl-1-hexen-3-yne with the formula: ##STR13## 1-hexene-3-yne withthe formula: ##STR14##

A second group of preferred ligands of the invention are those withformulas (II), (III) or (IV) in which X₁ and X₂, identical or different,are radicals with the following formula (VII): ##STR15## in which R₆,R₇, R₈ have the same denotation as in formula (V) and n is 0 to 8 suchthat (C)n-R₆ remains a lower alkyl.

A third group of ligands of the invention are those comprising both analkoxy group and a group comprising a double bond each placed eitherside of the double bond, these ligands meeting formula (IV) in which X₁has the formula (V) and X₂ has the formula (VII) or the reverse.

In the above formulas, by lower alkyl is meant more particularly thealkyls at C₁ to C₈, linear or branched, such as --CH₃ or --C₂ H₅. Thesemay be substituted by one or more fluorine atoms such as the radicals:--CF₃, --C₂ F₅, --CH₂ CF₃, --CF₂ CH₃).

Other advantages and characteristics of the invention will becomeapparent in the following examples relating to the preparation andanalysis of copper complexes with the formula: ##STR16## in which L is2-methyl-1-hexen-3-yne or 1-hexene-3-yne which are compounds whosepreparation has already been described in the prior art and which areknown in particular as polymerization agents.

EXAMPLE 1

The ligand used in this example is 2-methyl-1-hexen-3-yne that iscommercially available. The copper complex was synthesized using amethod described in the prior art (P. Doppelt, T. H. Baum and L. Ricard,Inorg. Chem. 35, 1286, 1996). Its characteristics are as follows: Anal.Calculated for CuC₁₂ H₁₁ F₆ O₂ : C, 39.6; H, 3.05; F, 31.32; Cu, 17.3.Found: C, 40.0; H, 3.10; Cu 17.0. m.p.=15° C. IR (liquid between twoNaCl discs): 2983 (f), 2016.3 (f. C.tbd.C), 1671 (m), 1556 (m), 1531(m), 1490 (s), 1348(f), 1258 (F), 1203 (F), 1147 (F), 1104 (f), 917 (f),800 (m), 673 (m), 665 (m), 581 (m), cm⁻¹. ¹ H NMR (Bruker, 300 Mhz,CDCl₃, 20° C.): δ 1.34 (t, 9 Hz, CH₃), 2.07 (s, CH₃), 2.71 (q, 9 Hz,CH₂), 5.33 (s ═CH), 5.58 (s, ═CH), 6.18 (s, C--H hfac), ¹³ C NMR: δ13.74 (s, CH₃), 16.24 (s, CH₃), 23.73 (s, CH₂), 87.68 (s, C--H), 89.90(s, C.tbd.C), 95.76 (s, C.tbd.C), 117.82 (q, 315 MHz, CF₃), 121.54 (s,C.tbd.C), 178.12 (q, 32 Hz, C≈O).

EXAMPLE 2

The ligand used in this example is 1-hexene-3-yne which is notcommercially available but whose characteristics are known. Thiscompound was prepared by adapting a method described in the prior art(G. Eglinton and M. C. Whiting, J. Org. Chem. 3650 (1950). The coppercomplex was synthesized as in example 1, and its characteristics are thefollowing: m.p.=18° C. IR (liquid between two NaCl discs): 2986 (f),2944 (f), 2885 (rf), 2016.4 (f, C.tbd.C), 1641 (m), 1556 (m), 1531 (m),1472 (s), 1409 (m), 1348 (f), 1257 (F), 1202 (F), 1147 (F), 1102 (f),967 (f), 800 (m), 673 (m), 589 (m), cm⁻¹. ¹ H NMR (Bruker, 300 MHz,CDCl₃, 20° C.): δ 1.37 (t, 7.3 Hz, CH₃), 2.67 (qd, 1.5 and 7.5 Hz, CH₂),5.47 (dd, 1.5 and 10.7 Hz, ═CHH), 5.8 (dd, 1.5 and 16.9 Hz, ═CHH), 6.05(ddt, 16.9, 1.5 and 10.7 Hz, ═CH, 6.15 (s, C--H, hfac), ¹³ C NMR; δ13.49 (s, CH₃), 16.05 (s, CH₂), 83.72 (s, C.tbd.C), 89.77 (s, C--H),96.15 (s, C.tbd.C), 112.5 (s, ═CH), 117.8 (q, 315 Hz, CF₃), 121.91 (s,C═C) 178.27 (q, 32 Hz, C═O).

EXAMPLE 3

Analysis of the complexes in examples 1 and 2

With the NMR spectrum of the proton it is possible to determine thestoicheiometry of the complexes by comparing the peak integration of theligand and of H methine of hexafluoroacethylacetonate; this ratio isdefinitely 1 which confirms the structure of the complexes given inexamples 1 and 2.

The NMR spectra of ¹³ C lead to asserting that the copper is bound tothe triple bond by comparing the peaks of the free ligand and of thechelated ligand. The new complexes of the invention are much more stablethan the corresponding complex in which the ligand is 3-hexyne; in thelatter case it has been shown that the triple bond is capable ofchelating (hfac)CU+ ions to yield a much less stable complex. With thecomplexes of the invention, however, the triple bond is sufficientlydeactivated owing to the combining of two insaturations to prevent theformation of binuclear complexes.

The complexes of examples 1 and 2 are both yellow liquids at ambienttemperature. They have been successfully used as precursors to depositfilms of metallic copper by CVD. They offer both good volatility, andconsequent rapid growth of the copper film, and great stability atevaporation temperature. By way of comparison, for the complex inexample 1, the temperature of the bubbler was maintained at 65° C. withno detectable degradation after two periods of 12 hours.

What is claimed is:
 1. Complex compound of oxidised copper (+1)stabilised by a ligand for the gas phase chemical deposit of copperhaving the general formula (I): ##STR17## in which R' and R", identicalor different, are a lower alkyl, optionally substituted by one or morehalogen atoms, R is chosen from among a hydrogen atom, a halogen atom, alower alkyl optionally substituted by one more halogen atoms, and Lrepresents the ligand stabilising said complex, characterised in that Lis an alkyne of which the triple bond is partially deactivated by one ortwo groups slightly attracting the electrons carried by said alkyne suchas to make it incapable of chelating another metal.
 2. Complex accordingto claim 1, characterized in that L is an alkyne of which the triplebond is partially deactivated by two groups slightly attractingelectrons arranged either side of said triple bond.
 3. Complex accordingto claim 1, in which R' and R" identical or different, are a loweralkyl, optionally substituted by one or more halogen atoms, wherein thehalogen atoms are fluorine atoms.
 4. Complex according to claim 1, inwhich R is chosen from among a halogen atom, wherein the halogen atom isa fluorine atom.
 5. Complex according to claim 1, in which R is chosenfrom among a lower alkyl optionally substituted by one more halogenatoms, wherein the halogen atoms are fluorine atoms.
 6. Complex compoundof oxidised copper (+1) stabilised by a ligand for the gas phasechemical deposit of copper, characterised in that said ligand L meetsthe following formula (II): ##STR18## or formula (III) as follows:##STR19## or formula (IV) as follows: ##STR20## in which R₁, R₂, R₃ andR₄, identical or different, are chosen from among a hydrogen atom, alower alkyl substituted by one or more fluorine atoms, a --Si(R₅)₃ groupin which R₅ is a lower alkyl, i and j are 0 to 3 and X₁ and X₂,identical or different, represent a group that is slightlyelectron-attracting.
 7. Complex compound of oxidised copper (+1)stabilised by a ligand for the gas phase chemical deposit of copperaccording to claim 6, characterized in that said ligand meets one offormulas (II), (III) or (IV) in which X₁ and X₂, identical or different,are radicals with formula (V) as follows: ##STR21## in which R₆, R₇ andR₈ are chosen from among a hydrogen atom, a lower alkyl substituted byone or more fluorine atoms, a Si(R₅)₃ group in which R₅ is a loweralkyl, or in which R₆ and R₂ together or R₆ and R₁ together, or two R₆radicals together form a group having the following formula (VI):##STR22## in which R₉ and R₁₀ are chosen from among a hydrogen atom, alower alkyl substituted by one or more fluorine atoms, a Si(R₅)₃ groupin which R₅ is a lower alkyl, and k is 1 to 3 such as to form ligandshaving cyclical formulas.
 8. Complex according to claim 7, characterizedin that it meets formula (IV) in which X₁ and X₂ are of formula (V) andi or j is different from
 0. 9. Complex according to claim 7,characterized in that L is 2-methyl-1-hexen-3-yne.
 10. Complex accordingto claim 7, characterized in that L is 1-hexene-3-yne.
 11. Complexcompound of oxidised copper (+1) stabilised by a ligand for the gasphase chemical deposit of copper according to claim 3, characterized inthat said ligand meets one of formulas (II), (III) or (IV) in which X₁and X₂, identical or different, are radicals of formula (VII) asfollows: ##STR23## in which R₆, R₇, R₈ have the same denotation as inclaim 4, and n is 0 to
 8. 12. Complex compound of oxidised copper (+1)stabilised by a ligand for the gas, phase chemical despoit of copperaccording to claim 6, characterized in that said ligand meets formula(IV) in which X₁ and X₂ of formulas (V) or (VII) are different. 13.Complex according to any one of claims 6 to 9, characterized in that informulas (II), (III), (IV), (V), (VI) and (VII) the lower alkyls arechosen from among alkyls at C₁ to C₈ either linear or branchedoptionally substituted by one or fluorine atoms.
 14. Method for the gasphase chemical deposit of a metallic copper film on a substrate bycontact of said substrate with an organometallic copper precursorvolatile in gas phase, characterised in that a complex according to anyof claims 1 to 9 is used as said precursor.